Vaso-occlusion wires are used in treating vascular conditions in which it is desired to occlude a region of a vessel or an aneurism within a vessel. The wire is introduced by first positioning a catheter at the selected site to be occluded, then advancing the wire through the catheter and into the site. The wire itself is typically a soft wire coil which can assume a linear condition for advancement though the catheter, and assume a convoluted configuration designed to "fill" the vessel or aneurism into which the coil is introduced, as described for example in U.S. Pat. No. 4,994,069.
Commonly, the vaso-occlusion wire must be placed at a remote, small-vessel site which can be accessed only through a tortuous vessel path involving multiple vessel branches, sharp turns at a vessel branch point, and/or small-diameter vessels, e.g., less than 2-5 mm. Such sites can be accessed only with a flexible, small-diameter catheter, e.g., a polyethylene-tube catheter having a distal-end inner diameter of 10-30 mils. Such a catheter is typically guided through a tortuous vessel by a guidewire having a bent tip whose direction can be controlled, to steer the catheter along a selected path.
After the catheter has been placed at the intended site, the guidewire is removed and the catheter is loaded with a vaso-occlusion wire, which is then advanced through the catheter with a pusher. When the wire is advanced beyond the end of catheter at the vaso-occlusion site, it assumes its convoluted shape designed to fill the vessel space into which it is placed.
One limitation of the above vaso-occlusion method just described is the difficulty in controlling the orientation and position of the wire in the vessel, or aneurism, after it is ejected from the catheter. For example, the wire may fail to anchor itself firmly in the vessel, and thus be carried by blood flow to a site downstream of the intended vaso-occlusion site. In addition, the wire may improperly orient itself at the site, producing incomplete vaso-occlusion. In either case, the vaso-occlusion procedure may be only partially effective.